Design And Experiment Of Spray Device For Dwarf Dense Planting Jujube Orchard

In the process of jujube production management,plant protection spraying is the key link to ensure stable and increased yield of jujube.At present,there are few plant protection spraying machines suitable for jujube orchards,and there are problems such as high labor intensity,low adhesion rate and poor penetration in spraying operation.It is important to improve the mechanization level of spraying operation in jujube orchards to enhance the operation efficiency,improve the quality of spraying,and enhance the effect of pest control in jujube orchards.In this thesis,we designed a dwarf dense date palm orchard spraying device with two types of operation:spray bar spraying and wind-driven spraying,and carried out research on device design,optimization and field operation performance（droplet adhesion rate and penetration）through theoretical analysis,numerical simulation and field test:（1）Overall design of spray device for dwarf dense planting jujube orchard:Through researching the planting pattern and agronomic requirements of dwarf dense date palm plantation,we proposed the overall design of spraying device,determined the operation mode and structure size of the device.Based on the shape of date palm trees,we designed the spray bar structure,determined the fan parameters according to the operating space,and completed the design of the liquid circuit system and the design and selection of each component.（2）Simulation analysis of spray bar device:In order to verify the rationality and stability of the spray bar structure,Ansys finite element analysis software was used to conduct static analysis and vibration modal analysis of the spray bar in full-and half-envelope mode of operation.Among them,the maximum stress of the two working methods of the spray bar are 1.97 MPa and 1.69 MPa,the maximum strain of1.20×10^-5mm/mm and 9.15×10^-6mm/mm,respectively,are less than the material limit,the maximum deformation of 0.013 mm and 0.02 mm,respectively,have no effect on the work of the spray bar,the spray bar of the first to sixth order modal inherent frequency is greater than the road excitation 0.66 Hz,will not Resonance phenomenon occurs,the results prove that the strength of the spray bar structure as well as stability to meet the needs.（3）Spraying operation flow field analysis:Based on CFD technology to simulate the spray bar fog field and wind-fed air flow field,using Fluent software to simulate the spray bar spray and wind-fed spray respectively,to obtain the droplet distribution pattern and air flow motion characteristics at different spraying distances,including droplet motion trajectory,droplet velocity,air flow velocity,pressure distribution,etc.To determine the reasonableness of the spraying distance in the range of 0.4-0.8 m for rod spraying and 1.2-2.0 m for airborne spraying,to provide a basis for optimizing the operating parameters of the device.（4）Field spraying tests:Based on the response surface experimental design method,tests were conducted for spray bar spraying and airborne spraying to analyze the effects of various factors on spray adhesion rate and penetration,and to obtain the optimal combination of working parameters for the two spraying modes:spray bar spraying operating speed of 1 m/s,nozzle pressure of 0.96 MPa,and spraying distance of 0.4 m,and airborne spraying operating speed of 1 m/s,nozzle pressure of 0.99 MPa,and spraying distance of 1.22 m.The working parameters were verified.The experimental verification of the working parameters showed that the average adhesion rate of spray bar spray was 78.68%and the penetration（coefficient of variation）was 21.42%,and the average adhesion rate of wind spray was 71.64%and the penetration（coefficient of variation）was 8.27%,which were basically consistent with the predicted values.The device has good operating effect,and the quality of spraying operation is effectively improved by choosing the appropriate operation method.